Influence of packaging film permeability and residual sulphur dioxide on the quality of pre-peeled potatoes

The effects of sodium bisulphite concentration and gas permeability of the packaging film on the surface colour, texture, exudate production and microbial growth of pre-peeled refrigerated potatoes were evaluated to determine shelf-life and the lowest level of preservative which could be used.
The product was packaged in polyethylene film, or in vacuo , using EVA-SARAN-EVA laminate and stored refrigerated. Polyethylene was not adequate in several aspects; packaging in oxygen barrier film allowed reduction of bisulphite levels, and vacuum packaging of 50 ppm bisulphite treated samples doubled the shelf-life of the product compared with aerobic packaging.     

MIXTURES OF BEEF TRIPE, BEEF LIVER AND SOYBEANS APPLIED TO FOOD DEVELOPMENT

A nutritive sausage‐type product was developed with beef tripe, beef liver and soybeans as ingredients. A three‐component mixture design was used to obtain seven different formulations (minimum of each main ingredient: 16.5%, maximum: 67.0%). Ingredients were ground, mixed and packed tightly with a polypropylene film to obtain a roll. Pieces were cooked in boiling water for 90 min. The composition of the obtained products varied within the following ranges: proteins 17.32–25.56 g/100 g, lipids 3.22–3.87 g/100 g, crude fiber 1.50–4.50 g/100 g, minerals 1.44–2.72 g/100 g. Total iron levels varied between 1.39 and 2.98 mg/100 g and calcium levels between 15.07 and 34.01 mg/100 g. Surface response analysis was applied to parameters obtained from texture profile analysis (hardness, adhesiveness, cohesiveness and elasticity). Products hardness increased when the soy content increased; on the contrary, formulations enriched in beef tripe were those of higher elasticity and cohesiveness. Color was mainly determined by the incorporation of liver. A nontrained panel was used to evaluate the acceptance of the different formulations. The most accepted one was that with equal proportions of the three main ingredients. Microbiological challenge testing showed that the thermal treatment was enough for assuring the product safeness even in samples with high initial microbial charge.     

SHELF-LIFE OF FRESH FILLED PASTA. HAZARD ANALYSIS AND CRITICAL CONTROL POINTS OF THE MANUFACTURING PROCESS AND HOUSEHOLD PRACTICES

Hazard Analysis and Critical Control Point (HACCP) approach was used to assess the safety of a fresh filling pasta (ricotta-filled ravioli) manufacturing plant in La Plata region, Argentina. Household practices like cooking and holding meals before serving were also evaluated. Samples of ricotta, main raw material of the filling, showed colony counts of Enterobacteriaceae total microorganisms, molds and yeasts of (5 × 10³-1 × 10⁵), (1x10⁵−1x10⁸) and 1 × 10⁵ CFU/g, respectively. E. coli was also detected in one out of five samples, suggesting a hazardous condition of this raw material. Salmonella spp. was not isolated from any of the dough samples tested. Ricotta filling showed high colony counts of mesophilic microorganisms (6 × 10⁶ CFU/g), Enterobacteriaceae (1 × 10⁵ - 1 × 10⁶ CFU/g), while E. Coli was detected in 20% of the samples. Counts of B. cereus, S. aureus were less than 1 × 10² CFU/g in the analyzed materials. In the finished product (ricotta-filled ravioli), the colony counts of mesophilic microorganisms and Enterobacteriaceae were 3 × 10⁸ and 8 × 10⁵ CFU/g, respectively. Critical Control Points found were cooking and holding time before serving. The implementation of suggested corrections allowed the microbial quality of the final product (ricotta-filled ravioli) to be improved considerably. The growth of total microbial counts during refrigerated storage (0, 4, 8 and 10C) were measured and the shelf-life of ricotta and ricotta-filled ravioli was calculated.     

MODELING OF MICROBIAL GROWTH IN REFRIGERATED DOUGHS FOR "EMPANADAS" WITH POTASSIUM SORBATE AND WHEY PROTEIN CONCENTRATE

Dough for "empanadas", a traditional meal in Argentina, are sold refrigerated with the addition of preservatives. The replacement of a small percentage of flour by whey protein concentrate (WPC) improves the color and acceptability of the "empanadas", but can decrease the shelf-life due to the microorganisms incorporated with the WPC. In this work the effect of the addition of two selected concentrations of potassium sorbate (0.067 - 0.134%) to dough for "empanadas" prepared with and without WPC on yeast growth (predominant microorganisms in this product) during refrigeration storage was investigated. Gompertz equation and kinetic parameters as specific growth rate (μ), lag phase duration (LPD), maximum population density (MPD) and activation energies from an Arrhenius-type expression, were estimated. The addition of potassium sorbate increased the storage-life of the dough for "empanadas", prepared with and without WPC, three-four times. The effect of potassium sorbate was more important at the higher concentration assayed. Results allow to predict the growth of yeast in different samples of dough stored between 0 and 10C.     

MATHEMATICAL MODELING OF MICROBIAL GROWTH IN FRESH FILLED PASTA STORED AT DIFFERENT TEMPERATURES

Growth curves for a selection of pertinent microorganisms in ricotta and ricotta-filled ravioli were analyzed in terms of Gompertz's model. The growth of Enterobacteriaceae, molds and yeasts and psychrotrophic microorganisms during storage at 0, 4, 8 and 10C was determined. Lag phase duration and specific growth rate were inversely related. The activation energies from an Arrhenius-type equation were calculated for the microorganisms under study. For ricotta samples, molds and yeasts were the most sensitive organisms showing E_μ values of 74.60 KJoule/mol while Enterobacteriaceae and psychrotrophic microorganisms had E_μ values of 24.30 and 25.70 KJoule/mol, respectively. For ricotta-filled ravioli samples, the three microorganisms showed activation energies in the range of 31.47–32.99 KJoule/mol; hence the temperature dependence of their growth rates was comparable. Results allow to predict microbial growth of different microorganisms in ricotta and ricotta-filled ravioli when exposed to different storage temperatures.